The present invention relates to new combination vaccine formulations. Combination vaccines (which provide protection against multiple pathogens) are very desirable in order to minimise the number of immunisations required to confer protection against multiple pathogens, to lower administration costs, and to increase acceptance and coverage rates. The well-documented phenomenon of antigenic competition (or interference) complicates the development of multi-component vaccines. Antigenic interference refers to the observation that administering multiple antigens often results in a diminished response to certain antigens relative to the immune response observed when such antigens are administered individually.
Combination vaccines are known which can prevent Bordetella pertussis, Clostridium tetani, Corynebacterium diphtheriae, and optionally Hepatitis B virus and/or Haemophilus influenzae type b (see, for instance, WO 93/24148 and WO 97/00697).